An exhaust turbo supercharger is provided that is able to effectively prevent exhaust gas that has flowed into between a turbine housing and a bearing housing from leaking to outside of the device, while allowing an excellent level of workability in assembly and disassembly. Included is a turbine housing, into which exhaust gas from an internal combustion engine is introduced; a turbine wheel which is provided within the turbine housing and which is rotation-driven by the exhaust gas; a turbine shaft, one end of which is inserted into the turbine housing, and to which the turbine wheel is attached; a bearing which supports the turbine shaft; and a bearing housing which is connected to the turbine housing and inside of which the bearing is housed. A bolt insert hole is formed in the turbine housing, and an internal thread insert made from a heat insulating material is provided in the bolt insert hole, and the turbine housing and the bearing housing are fixed by a bolt that engages with the internal thread insert.